Relay with chatter preventing shunting circuit



Dec. 24, 1968 M. A. TABET RELAY WITH CHATTER PREVENTING SHUNTING CIRCUITFiled March 9. 1966 4 TE Fl 6. 2 /9 "'"IO "2L? LOAD 28 29 J 27% k 55 wFIG. 3

Ma k I7LL/ 32 3/ M 2/ x LOAD I INVENTOR MICHAEL A. 74857 ATTORNEY UnitedStates Patent 3,418,537 RELAY WITH CHATTER PREVENTING SHUNTING CIRCUITMichael A. Tahet, 1336 Ballentine Blvd., Norfolk, Va. 23504 Filed Mar.9, 1966, Ser. No. 533,072 2 Claims. (Cl. 317123) ABSTRACT OF THEDISCLOSURE An energy-absorbing element in parallel circuit relationshipwith a relay. The energy-absorbing element is taken out of the circuitby a first set of contacts actuated upon initial energizaiion of therelay. Upon the elimination of the shunting energy-absorbing element inthe circuit a load set of contacts are actuated.

The present invention relates to a magnetically actuated relay equippedwith contacts for opening and closing a load circuit and the inventionmore specifically pertains to control means in combination with such arelay for preventing chatering of the contacts during opening andclosing of the load circuit in response to gradual changes in thevoltage applied to the operating coil of the relay.

In operation of such a relay and when there is a relatively slowincrease in the voltage applied across the operating coil there is agradual development of flux and eventually the armature is moved fromits inactive position but because of the slow rise in voltage thearmature is not shifted to its fully actuated position and there ischattering or fluttering of the contacts. A similar condition developswhen voltage impressed across the operating coil slowly decreasesbecause the flux does not collapse abruptly. Chattering of the contactsis particularly pronounced when the relay is operated with alternatingcurrent. Vibration or chattering of the contacts in making or breaking aload circuit causes deterioration of the contacts and often providesunsatisfactory operation of equipment forming a part of the loadcircuit.

It is an object of the present invention to provide means for shuntingsome of the energy from the operating coil of a relay to preventpremature movement of the armature to thereby provide an additionalperiod of time for a voltage level to be attained which will developsufiicient current through the operating coil of the relay before thearmature is moved from its inactive position and to prO- vide forrendering the shunt inoperative with the result that all of the energyis then applied to the operating coil whereby the armature is abruptlyshifted to its full actuated position to provide for snap operation ofthe contacts which control a load circuit.

Another object of the invention is to provide an energy-absorbingelement in parallel circuit relationship with the operating coil of arelay so that some current is diverted from the operating coil while thevoltage applied thereto slowly increases in value including means tointerrupt the parallel circuit upon initial movement of the armaturefrom its inactive position whereby the armature then abruptly moves toits fully actuated position to positively close or open the loadcontrolling contacts with the assembly insuring re-establishment of theenergy-absorbing circuit as the armature initiates its return to theinactive position.

A more specific object of the invention is to provide anenergy-absorbing element such as resistance, condenser, or inductance inparallel circuit relationship with the operating coil of a relay so thatwhen the armature first moves from its inactive position contacts in theparallel circuit disconnect the energy-absorbing element whereby theentire voltage which is then available will then be applied across theoperating coil of the relay for shifting the armature to its fullactuated position with the unit so arranged that energy-absorbingelement is placed in parallel relationship with the operating coil uponinitial movement of the armature from its fully actuate-d position.

Other objects and features of the invention will be appreciated andbecome apparent to those skilled in the art to which the inventionpertains as the present disclosure proceeds and upon consideration ofthe accompanying drawing taken in conjunction with the followingdetailed description wherein an embodiment of the invention isdisclosed.

In the drawing:

FIG. 1 is a fragmentary side elevation view of elements of a relayforming a component of the invention.

FIG. 2 is a circuit diagram of a combination which embodies theinvention and showing relay elements of FIG. 1.

FIG. 3 is a view similar to FIG. 2 wherein the contacts of the relay forcontrolling the load circuit are normally open.

The invention pertains to means for controlling the operation of a relaywhich may take various forms and in the embodiment shown in the drawingthe operating coil is indicated at 10. An electrical source of generallyfixed voltage is indicated at 11. The relay is equipped with an armature12 which is in an inactive position when the operating coil 10 isdeenergized. A relatively rigid bar 14 is mounted in any suitableinsulated manner on the relay frame. A contact 17 carried by the bar 14is adapted for cooperation with a contact 18 carried by a resilientblade 19 which is mounted in an insulated relationship with respect tothe relay frame. The contacts 17 and 18 are for controlling a loadcircuit which extends from one side of the source 11 through a conductor21, a conductor 22, the contacts 17 and 18, the blade 19 and to theother side of the electrical source.

A unit embodying the invention has particular utility when theelectrical source has a substantially fixed voltage and control of therelay is carried out by voltage varying means such as an adjustableresistor or impedance 26 which varies slowly whereby its ohmic orimpedance value is altered by small increments over a protracted period.The voltage varying means 26 may take the form of a photoelectricalelement the resistance of which decreases when light falling thereonincreases and the resistance of which increases when light falling onthe photoelectric element decreases.

A unit for controlling a load circuit and exhibiting the inventionincludes a second set of normally closed contacts 27 and 28. The contact27 is carried by the resilient blade 19 while the contact 28 is carriedby another spring type blade 29 mounted in an insulated manner on therelay frame. A stud 31 formed of insulating material is arranged to beshifted by the armature 12 and a nose portion 33 on the stud engages theblade 29 to move the contact 28 from engagement with the contact 27 uponinitial movement of the armature from its inactive position. During thisinitial movement of the stud the normally closed contacts 17 and 18remain in engagement.

A circuit shunts the operating coil 10 and includes an energy-absorbingelement 36 such as a resistor. The energy-absorbing element may take theform of a condenser or inductance when the operating supply isalternating current. The shunt circuit extends from one side of thesource 11 through the normally closed contacts 27 and 28, the blade 29and the energy-absorbing element 36 to the other terminal of theoperating coil 10. The energy-absorbing element 36 is thus in parallelcircuit relationship with the operating coil 10. The impedance of thecoil in relation to resistance or impedance of the energy-absorbingelement 36 is such that a major portion of the current flows through theoperating coil 10. In one satisfactory embodiment approximatelyone-fourth of the current flowing in the circuit bypasses the operatingcoil 10.

When the armature is in the inactive position and upon the occurrence ofa slow change of the voltage varying means current flows through theoperating coil 10 and a minor portion of the current flows through theenergyabsorbing element 36 which is then in parallel circuitrelationship with the operating coil 10. If the voltage varying means isan adjustable resistor and as its ohmic value is slowly decreasedsufiicient flux is developed by the coil 10 to move the armature 12 fromits inactive position. Such initial movement of the armature causes thenose portion 33 of the stud 31 to move the contact 28 from engagementwith the contact 27. The bypass circuit is thereby interrupted and allof the current then flows through the operating coil 10 and the armature12 shifted abruptly to its fully actuated position. During such movementof the armature a shoulder 32 on the stud 31 engages the blade 19 andmoves the contact 18 from engagement with the contact 17. Thus thecontacts controlling the load circuit are opened with abrupt action andchattering of the contacts 17 and 18 is avoided.

The unit also serves to prevent fluttering of the contacts duringclosing of the load circuit. As the voltage applied across the operatingcoil 10 slowly decreases the flux decreases but does not collapse.Eventually the armature 12 retreats slightly from its fully actuatedposition and the contact 28 then engages the contact 27. Such actionplaces the energy-absorbing element 36 in parallel circuit relationshipwith the operating coil 10 and a minor portion of the current then flowsthrough the shunt circuit. When the contacts 27 and 28 close there is apronounced decrease in the flux developed by the coil 10 whereby thearmature 12 abruptly moves to its inactive position by action of theresilient blade 29 and the blade 19 moves the contact 18, withoutchattering or fluttering into engagement with the contact 17 to energizethe load circuit.

The unit shown and described in connection with FIGS. 1 and 2 hasparticular utility when used on alternating current for controlling theenergization of a load such as a street lamp or lamps and when thevoltage varying means 26 is in the form of a photoelectric element ofthe broad area cadmium sulphide type. Such a photoelectrical element iscommercially available but has a limited energy handling capacity and ina range below three hundred milliwatts. The spring pressures of theblades 19 and 29 are then of low value of about sixty grams when thesupply source 11 is in the one hundred ten voltage range. Under suchconditions the chattering of the contacts 17 and 18 is pronouncedbecause of the slow and protracted changes in the resistance of thephotoelectric cell as a consequence of gradual changes in the naturallight Which occurs in the morning and evening hours. When the loadcircuit or lamp is energized the natural light falling on thephotoelectric element increases slowly in the morning so that thecurrent flowing through the operating coil 10 increases at a slow rateand over an extended period. Eventually the armature 12 moves slightlyfrom its inactive position. The nose 33 of the stud 31 then moves thecontact 28 from engagement with the contact 27 whereby theenergy-absorbing element 36 is no longer in parallel circuitrelationship with the operating coil 10. The armature 12 then movesabruptly to its fully actuated position and the shoulder 32 on the stud31 moves the contact 18 in a positive manner from engagement with thecontact 17. The lamp circuit is thus interrupted and the lamp isdeenergized without fluttering or chattering of the contacts whichcontrol the load circuit.

Such desired results are attained in the evening when the light fallingon the photoelcctrical element decreases which provides an increase inthe resistance 26. The armature in its initial movement from the fullyactuated position allows the blade 29 to move the contact 28 intoengagement with the contact 27. The shunt circuit then diverts currentfrom the operating coil 10 whereby the armature 12 abruptly moves to itsinactive position. The load contacts 17 and 18 are thereby closedwithout fluttering action to energize the load circuit.

A unit embodying the invention may include other relays such as the typeshown in FIG. 3 wherein the contacts 27 and 28 are normally closed butthe contacts 17a and 18a for controlling the load circuit are normallyopen. The resilient blade supporting the movable contacts 17a is adaptedto be engaged by the shoulder 32 on the stud 31 for closing the contacts17a and 18a after the contact 28 has been moved from engagement with thecontact 27. The contacts 27 and 28 close upon initial movement of thearmature from its fully actuated position. The armature then movesabruptly to its inactive position whereby the contact 17a moves withpositive action from the contact 18a.

While the invention has been described with regard to one general typeof relay wherein the contacts are supported by resilient blades whichserve to return the armature 12 to its inactive position changes may bemade in the structural features of the relay. Other alternations may bemade in the elements as well as the overall assembly without departingfrom the spirit and scope of the invention as set forth in the appendedclaims.

What I claim and desire to secure by Letters Patent is:

1. An electrical unit for opening and closing a load circuit comprising,a relay having an operating coil and an armature and first contactsengaged and disengaged upon movements of the armature for controlling aload circuit, an electrical source and means for varying the voltagethereof, means applying said variable voltage to said operating coil, acircuit including an energy-absorbing element therein and normallyclosed second contacts in parallel circuit relationship with saidoperating coil shunting a portion of the current developed by saidvariable voltage from the operating coil, and means actuated by initialmovement of the armature from its inactive position opening said secondcontacts whereby all of the current developed by said variable voltageis applied to said operating coil to abruptly actuate the firstcontacts.

2. An electrical unit for opening and closing a load circuit accordingto claim 1 wherein the means actuated by initial movement of thearmature from its inactive position is constructed and arranged toprovide for closing of the second contacts upon initial movement of thearmature from its fully actuated position whereby the parallel circuitand the energy-absorbing element divert current from the operating coilto provide for abrupt movement of the armature to its inactive position.

References Cited UNITED STATES PATENTS 1,242,763 10/1917 Bossu 3171231,246,687 11/1917 Wells 317123 LEE T. HIX, Primary Examiner.

J. A. SILVERMAN, Assistant Examiner.

